The 22Rv1 cell line is widely used for prostate cancer research and other studies throughout the world. These cells were established from a human prostate tumor, CWR22, that was serially passaged in nude mice and selected for androgen independence. The 22Rv1 cells are known to produce high titers of xenotropic murine leukemia virus-related virus (XMRV). Recent studies suggested that XMRV was inadvertently created in the 1990's when two murine leukemia virus (MLV) genomes (pre-XMRV1 and pre-XMRV-2) recombined during passaging of the CWR22 tumor in mice. The conclusion that XMRV originated from mice and not the patient was based partly on the failure to detect XMRV in early CWR22 xenografts. While that deduction is certainly justified, we examined the possibility that a closely related virus could have been present in primary tumor tissue. Here we report that we have located the original prostate tumor tissue excised from patient CWR22 and have assayed the corresponding DNA by PCR and the tissue sections by fluorescence in situ hybridization for the presence of XMRV or a similar virus. The primary tumor tissues lacked mouse DNA as determined by PCR for intracisternal A type particle DNA, thus avoiding one of the limitations of studying xenografts. We show that neither XMRV nor a closely related virus was present in primary prostate tissue of patient CWR22. Our findings confirm and reinforce the conclusion that XMRV is a recombinant laboratory-generated mouse virus that is highly adapted for human prostate cancer cells.

XMRV (xenotropic murine leukemia virus-related virus) was initially discovered in association with prostate cancer and later with chronic fatigue syndrome (CFS). Its association with CFS is now largely discredited, and current results support a laboratory origin for XMRV with no reproducible evidence for infection of humans. However, some results indicating the presence of XMRV in prostate cancer are difficult to attribute to sample contamination. Here we have sought biological evidence that might confirm the presence of XMRV in prostate cancer samples previously having tested positive.

Methods and Results
We have tested for infectious XMRV and neutralizing antibodies against XMRV in blood plasma from 29 subjects with prostate cancer, and for infectious XMRV in prostate secretions from another five prostate cancer subjects. Nine of these subjects had previously tested positive for XMRV by PCR or by virus assay. We did not detect XMRV or related retroviruses in any sample, and the neutralizing activities of the plasma samples were all very low, a result inconsistent with XMRV infection of the plasma donors.

Conclusions
We find no evidence for XMRV infection of any human subject tested, either by assay for infectious virus or for neutralizing antibodies. Our results are consistent with the majority of published studies on XMRV, which find that XMRV is not present in humans. The observed low to undetectable XMRV neutralization by human plasma indicates a lack of innate restriction of XMRV replication by soluble factors in human blood.

Abstract Top
Background:
Xenotropic murine leukemia virus-related virus (XMRV) was generated after a recombination event between two endogenous murine leukemia viruses during the production of a prostate cancer cell line. Although the associations of the XMRV infection with human diseases appear unlikely, the XMRV is a retrovirus of undefined pathogenic potential, able to replicate in human cells in vitro. Since recent studies using animal models for infection have yielded conflicting results, we set out an ex vivo model for XMRV infection of human tonsillar tissue to determine whether XMRV produced by 22Rv1 cells is able to replicate in human lymphoid organs. Tonsil blocks were infected and infection kinetics and its pathogenic effects were monitored

Results:
XMRV, though restricted by APOBEC, enters and integrates into the tissue cells. The infection did not result in changes of T or B-cells, immune activation, nor inflammatory chemokines. Infectious viruses could be recovered from supernatants of infected tonsils by reinfecting DERSE XMRV indicator cell line, although these supernatants could not establish a new infection in fresh tonsil culture, indicating that in our model, the viral replication is controlled by innate antiviral restriction factors.

Conclusions:
Overall, the replication-competent retrovirus XMRV, present in a high number of laboratories, is able to infect human lymphoid tissue and produce infectious viruses, even though they were unable to establish a new infection in fresh tonsillar tissue. Hereby, laboratories working with cell lines producing XMRV should have knowledge and understanding of the potential biological biohazardous risks of this virus.

Quote
Recently, the presence of several MLV strains in over one fourth of xenograft cell lines has been documented [72], some of them releasing large number of infectious virions. This is the case of 22Rv1 cells, a high-titer XMRV producing cell line which should be carefully considered from the standpoint of possible horizontal spread to other human cells and biohazard of unknown potential to laboratory personnel [51]. Regarding the virus transmission to other cell lines, two cell lines that have become infected with XMRV in the laboratory by a contamination with the 22Rv1cell line have already been reported, confirming the highly infectious nature of this virus [72,73].

Concerning the potential biohazards to laboratory personnel involved in cell culture facilities, it is
important to explore XMRV infectivity and replication capacity in humans.

During the last year an enormous amount of data about the origin and the prevalence of XMRV have indicated that this virus has a recombinant origin and it is not circulating in the human population [11–17,23–33,36–47], although many questions about the biology and physiopathology of this virus remain still unclear.
Despite all these data and considering, i) the susceptibility of humans cells to the XMRV infection [53,101,102], ii) the contradictory data on experimental infection of macaques by XMRV [86,87], iii) the high-titer production of XMRV by the 22Rv1 cell line, widely used in laboratory, and iv) the existence of XMRV/human contacts in laboratory personnel involved in cell culture facilities,it could be relevant to develop new experimental models for the study of XMRV pathogenesis in humans alternative to the use of non-human primates.

XMRV, though restricted by APOBEC, enters and integrates into the tissue cells. The infection did not result in changes of T or B-cells, immune activation, nor inflammatory chemokines. Infectious viruses could be recovered from supernatants of infected tonsils by reinfecting DERSE XMRV indicator cell line, although these supernatants could not establish a new infection in fresh tonsil culture, indicating that in our model, the viral replication is controlled by innate antiviral restriction factors.

It suggests that XMRV can infect human cells. And does so without changes to T or B-cells, or inflammatory chemokines. Thus there might be a low or undetectable inflammatory reponse.

It also suggests that XMRV can live happily in human lymphoid tissue, even though the virus is possibly removed quickly from the blood. Many of us have speculated that this could be the case, and suggested that lymphoid tissue should be examined rather than the blood.

It also suggests that replication of fully functioning viruses would be at a very low rate, which would fit in with the disease nature of ME. (i.e. a smouldering virus replication.)

It was nice to see this acknowledged, since we have made this point here many times:

However, some results indicating the presence of XMRV in prostate cancer are difficult to attribute to sample contamination

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Although they found no XMRV in Miller's study, those results are still very difficult to explain by contamination, and nothing here or elsewhere has yet explained or really addressed that issue.

It's still very hard to explain why multiple studies found those differential percentages of positives between controls and patient samples - and at fairly consistent levels between those multiple studies, too - and I would hope that future investigations will aim to answer that question. The mystery and the controversy won't be resolved until that happens, and it also seems quite likely that the answer to that puzzle could be quite significant - and it's also likely that whatever the explanation is, it also has a bearing on what happened in the Lombardi study.

Well, when controls vs ME patients produce that quantative difference, then obviously it HAS ot be a reaction specific to the ME patients
whether that is actually a virus, or, the ME patients have so many viral particles that test are imprecise, or, auto-immune issues, or, "something unknown", or, a problem with the standard test methods
we simply don't know, but it does throw up a huge series of issues in any of those possibilities.

Conclusions:Overall, the replication-competent retrovirus XMRV, present in a high number of laboratories, is able to infect human lymphoid tissue and produce infectious viruses, even though they were unable to establish a new infection in fresh tonsillar tissue. Hereby, laboratories working with cell lines producing XMRV should have knowledge and understanding of the potential biological biohazardous risks of this virus. VillageLife, Yesterday at 8:07 PMOverall, the replication-competent retrovirus XMR present in a high number of laboratories, is able to infect human lymphoid tissue and produce infectious viruses....hmmm I am no expert and my brain doesn't work well (maybe because I am XMRV positive) but one and one is still TWO...right? If there is one retrovirus (XMRV) that is replication-competent then chances are high that there are other replication-competent retroviruses. Who knows. Although it was humane to put those sick XMRV infected Jaques down, I wonder what they would have shown us. More questions than answers really. I still can't understand why I have anti-bodies to XMRV in my body. Just my my humble opine.

DERSE detects XMRV a lot but doesnt detect anything else. even the ruscettis no longer believe in xmrv.

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Are you certain about all of that Daffodil?
You've made four very interesting statements, none of which I was previously aware of...
Would you mind sharing your evidence, or pointing us towards it, please?
I'm sure many of us would really appreciate it.

So you can't point us towards any evidence relating to any of your four statements?
But without evidence, it's just hearsay.

Just to recap what you said:
1. XMRV antibody tests are meaningless.
2. Lipkin has carried out next generation sequencing in relation to XMRV antibodies.
3. DERSE is only able to detect XMRV.
4. The Ruscettis no longer believe in XMRV.

Without evidence to back it up, I'd dispute all of these assertions, except no. 3, for the following reasons:

1. XMRV-related antibodies have not yet been disputed by anybody publicly. Even Maureen Hanson detected these and confirmed that they merited further investigation.
2. As far as I am aware, Lipkin has not yet started his pathogens study, and he's not personally carrying out any actual research in the XMRV study.
3. DERSE is designed specifically to detect XMRV, so there would be a problem if it was detecting other viruses.
4. XMRV is an undoubted fact (or at least, there is a general consensus that XMRV is a novel virus). And the Ruscettis have been working with actual XMRV viruses for ages.

You know that DERSE just detects XMRV? Well, that's what it's designed to do. So there's nothing new there.

You know that the Ruscettis don't believe in XMRV? But XMRV is an established fact. Or at least, that's the scientific consensus. It's a novel retrovirus.

You know that Lipkin is looking for XMRV antibodies? But he hasn't started his pathogen study yet, so he won't even have started looking for them yet. (Or has he? Am I wrong about that?)

You know that XMRV antibodies are meaningless. Based on what? Even if the antibodies turn out not to be XMRV-related, they may still be a relevant biomarker. So has Lipkin (allegedly) decided that the antibodies were a laboratory artefact, or a biomarker unrelated to XMRV? To date, the antibodies have been confirmed by Maureen Hanson, and possibly other researchers (my memory is vague about that), so even if further research has been carried out, I doubt if there is yet a consensus on the relevance of the antibodies, unless someone has come up with excellent evidence, and a convincing conclusion.

I understand it if you can't reveal any sources, but could you at least tell us if this source is an established researcher or someone like Gerwyn/Ronald Roberts/V99. Without revealing any sources, I believe it's important to know from which direction this is coming.